A simplified rewrite of code I'm using to add and remove a class on a website header to indicate when the page is scrolled to the top. Untested since rewrite, but should work if I haven't made typos.

gistfile1.js

(function(win, $){

	$(document).ready(function(){

		var scroll_class = 'scrolled-top';
		var scroll_timer;
		var $win = $(win);
		var $head = $('#head');

		$win.on('scroll', function(){
			// you may want to throttle this callback
			// (although I decided not to bother)
			clearTimeout(scroll_timer);
			scroll_timer = setTimeout(function(){
				// fire a custom event once scrolling has ceased for 300ms
				$win.trigger('scrollended');
			}, 300);
		});

		// set 'scrollended' custom event handler
		$win.on('scrollended', function(){
	        // Start with 'scrolled-top' on head element onload (in actual html, maybe).
	        // Remove when scrolled beyond 5px. Re-add it otherwise.
			if ($win.scrollTop() > 5) {
				$head.removeClass( scroll_class );
			} else {
				$head.addClass( scroll_class );
			}
		});

	});

})(window, jQuery);